When is the shortest day of the year?

It has been cold for many weeks far north of the equator, but astronomically the winter season only begins when the solstice occurs. It happens this Saturday, when the Northern Hemisphere has its shortest day and longest night of the year, and the Southern Hemisphere has its longest day and shortest night of the year.

Here’s everything you need to know about this week’s solstice — and why it matters.

Winter solstice 2024: Time and date

The winter solstice in the northern hemisphere (and the summer solstice in the southern hemisphere) takes place on Saturday, December 21 at 4:19 AM EST. At the exact moment, the sun shines above the Tropic of Capricorn. It appears at its southernmost point seen from the Northern Hemisphere.

“The word solstice comes from the Latin words sun sun and sister (to stand still),” Shyam Balaji, a researcher in astroparticle physics and cosmology at King’s College London, said in an email. “It refers to the point at which the sun’s apparent north or south motion stops before it reverses.”

Winter Solstice 2024: Why it’s happening

“The December solstice occurs because the Earth is tilted on its axis by about 23.5 degrees relative to its orbit around the sun,” Balaji said. “This tilt causes different parts of the Earth to receive different amounts of sunlight throughout the year. During the December solstice, the northern hemisphere is tilted furthest away from the sun, resulting in the shortest day and longest night of the year for that hemisphere.”

The sun is also lower in the sky and takes a shorter path through the sky. See cold temperatures in the Northern Hemisphere.

Winter Solstice 2024: Earth at ‘Perihelion’

The seasons are related to what the Earth is called and have nothing to do with how close the Earth is to the sun. Earth will reach perihelion – the closest it will come to the sun in its slightly elliptical orbit – on January 3, 2025, just two weeks after the solstice.

Instead, the winter solstice marks the moment when the sun is above the Tropic of Capricorn, after which the days begin to get longer. So the winter solstice is generally celebrated as being the rebirth of the sun and as the beginning of the solar year.

Winter solstice 2024: How long is the shortest day of the year?

The length of the shortest day varies depending on your location on the planet. Here are some examples from the Northern Hemisphere:

• New York: 9 hours and 15 minutes.
• Los Angeles: 9 hours and 53 minutes.
• London: 7 hours and 49 minutes.

“The exact duration will vary based on how far north or south you are from the equator,” Balaji said. “After the December Solstice, the days begin to get longer in the Northern Hemisphere.”

I wish you clear skies and big eyes.